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2012 astorb.dat 3MS3 IKI 2012 (1)the percentage of comet-like orbits (higher impact velocities) on the Moon is about 25% to 20%, on Mars this number is factor of ~2 less; (2) at the modern Mars orbit (e=0.094) the “bolide ratio” (the ratio of impact number per unit area per unit time) is about R b =5.5 in comparison with 2000 estimates of R b =4.9 (3) the average impact velocity for asteroid-like objects on the moon increases to ~19 km/s in comparison with 16.1 km/s in 2000 estimates.

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2012 astorb.dat, Mars- and Moon-cossers number vs. magnitude (H=18 approximately corresponds to Dproj ~ 1 km In the current epoch number of Mars-crossers with asteroid like orbits is factor of 20 larger than the number of Moon-crossers. Number of bodies with comet-like orbits is factor of 5 larger for Mars. 3MS3 IKI 2012

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From craters to projectiles Scaling laws for impact cratering allow us to convert size-frequency distribution of craters to the size-frequency distribution of projectiles Crater-derived curves may be compared with astronomical observations 3MS3 IKI 2012

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2008 iteration of the scaling law for small (<1-10 km) lunar craters Blind usage of “standard” scaling laws results in a factor of 6 difference in the R(D_crater) for the same projectile. Looks strange... 3MS3 IKI 2012

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Conclusions 3MS3 IKI 2012  We are close to update the 2000 Mars/moon cratering rate ratio… but not ready yet.   Pure updating of planetary-crosser’s orbit list of crossers does not change the Mars/moon impact ratio dramatically (despite ~6-fold increase in the number of known objects).  Future discussion should include possible difference in crater- forming projectile properties. Small crater clusters found on Mars witness in favor of the presence of 10% to 20% low density (high porosity?) projectiles.  Two additional questions: (1) the difference in mechanical properties of regolith on the dry Moon and possibly ice-saturated Martian soil, and (2) the efficiency of lunar impacts of low-density objects assumed from Martian strewn fields.  New observational data demands new supportive research and modeling.

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Asteroids, Trojan, and JF comets (2) R-plot for Main Belt asteroids according to Davis et al. (1994) and Spacewatch data by Jedicke and Metcalfe (1998) for all the Main Belt and the inner belt in comparison with the SFD for projectiles formed lunar craters. Trojans are after Jewitt et al. (2000), comets - after Tankredy et al. (2000). 3MS3 IKI 2012